A compelling, twisting and shocking documentary, English director Tim Wardle's Three Identical Strangers is one of those "incredible but true" stories that's great to talk about with friends or read up on after the fact. It also raises more than the usual spoiler issues.

Talking about the film in any detail feels somewhat akin to handing you a gift-wrapped present and saying, "I hope you like it -- It's a thriller about a diabolical secret experiment."

Let's start with what facts are already well-known to many people and therefore, fair game. In 1980, three 19-year-olds from the New York area, Robert Shafran, Eddy Galland and David Kellman, discovered they were identical triplets who had been adopted by different families.

Edward Galland, David Kellman and Robert Shafran share an even stranger past than we thought.

The three boys looked like dolls off the same assembly line -- with matching halos of curls, toothy grins and big-chested wrestlers' bodies. Gregarious and high-spirited, they made the rounds of TV shows from Phil Donahue to Ted Koppel. People adored them and their amazing similar tastes in cigarettes and women, proof, apparently, of the amazing power of genetics. The boys hit Studio 54 and appeared in a cameo in Desperately Seeking Susan. They shared an apartment and went into business, starting a steak-house restaurant called Triplets.

The premise screams wacky ‘80s sitcom (I see maybe, John Stamos or Joey Lawrence in triplicate). It’s an impression enhanced by Wardle's jaunty editing, music choices (Walking on Sunshine) and somewhat kitschy re-enactments. But after a period of elation, some cracks appear between the siblings and their back stories.

Not that circumstances of their birth were particularly mysterious. They learn that their conception was the result of a "prom night knock-up" of their teen-aged mother. They were born at the Long Island Jewish Medical Center and shortly after, placed with families - one wealthy, one middle-class and one working-class - by Louise Wise Services, a prominent adoption agency for Jewish children. It took a while before anyone thought to ask: Why were they separated in the first place?

The answer to that puzzle, again on the public record, comes from a New Yorker story from 1995 by Lawrence Wright, in an article on twins - catnip for scientists pursuing nature-nurture experiments. In his research, Wright (who is interviewed extensively in the film) learned of an unpublished study by a psychiatrist, an Austrian-Jewish Holocaust refugee, who hired the now-closed Louise Wise company to supply him with unwitting test subjects, including several sets of twins as well as the triplets.

Wardle's film picks up where the Lawrence Wright's research left off. The filmmaker Wardle interviews the three men, who grow less like each other in appearance as they age. They suffer shocks, set-backs and, in one case, tragedy. The film’s tone shifts to a series of one-on-one interviews, like a police procedural uncovering a horrible injustice.

In both its light and dark phases, Three Identical Strangers comes across as almost too calculatedly entertaining, as Wardle carefully deals out the critical information, with the odd red herring, for maximum effect. In its defense, the film is consistently compassionate and fair-minded. Ultimately, the film confirms its investigative legitimacy by refusing to offer easy answers.

Were the researchers looking for specific mental health issues? How much did they control the family lives of their subjects? That critical information remains sealed in a Yale archive until 2065, unless a lawsuit can shake the data loose. Then, perhaps, the subjects, and the rest of us, can understand how the triplets' lives were shaped by their DNA, and how much by nurture, including the meddling of unethical scientists.

Three Identical Strangers. Directed by Tim Wardle. With Bobby Shafran, David Kellman and Lawrence Wright. Three Identical Stranger is showing at the Cineplex Varsity Cinema.